Separation of solids from fluids



March 24, 1959 s. 1:.y LAwsoN SEPARATION oF soLIDs FROM FLUIDs Filed Aug. 15, 1954 aaddlals INVENTOR.A

S D LAWS ON www AT TORNEYS i l l as/9,224 SEPARA'I'IQNOF SOLIDS FROM FLUIDS Shelby D. Lawson, Bartlesville, Okla., assignor to 'Phillips Petroleum Company, a corporation of Delaware Application August 13, 1,954, Serial No. 449,648 18 Claims. (Cl.'20S.-x10 0) This invention relates to the separation of solids from fluids. In one aspect thisvinvention relates to a method for separating nely divided solids from admixture with a fluid, by passing a displacing or flushing fluid in countercurrent flow contact relation with a body of the solidsfluid so as to displace fluid initially in Contact with the solids. In one aspect this invention relates to a method for separating nely divided solids from'admixture with a fluid, by passing afbody of the solids-iiuid into a settling zone and passing a displacing or flushing fluid upwardly into the said body in uniformcontact therewith at a controlled rate of flow so as to displace the uid initially present but not to preclude settling of solids from the said solids-huid body. vIn one aspect this invention relates to the separation of finely divided solids from ,admixture with a liuid not easily separabletfrom said solids, by displacing the fluidi from the said admixture employing a iiushing or displacing fluid therefor, and distilling flushing fluid from the residual-solids. Inanother aspect this invention relates tothe catalytic conversion of reactant materials. separation of undesirable oil by-product from admixture with catalyst from a hydrocarbon conversion step, by countercurrently contacting such a catalyst-oil mixture with a ushing or displacing liquid so as to permit replacement of the by-product oil with ilushing liquid and so as to permit settling of catalyst from the zone of contact. In still another aspect thisinvention relates to a iluid catalytic hydrocarbon cracking process wherein catalyst is recovered from eilluents Yas a slurry with a high coke-yielding oil, i.e., an oil easily cokable under the cracking conditions, and the'latter is displaced from the slurry, lby passing the said slurry into `a settlingzone and passing a low cokeyielding oil, i.e. one that is less easily cokable under the cracking conditions into the said slurry in contact therewith under controlled conditions of time and uniformity of contact to permit replacement of the high coke-yielding oil withv the said 'less easily cokable oil and so as to allow settling of the catalyst particles from the zone of the said contacting as a slurry with the low cokeyielding oil, and wherein catalyst,in forming the latter slurry, is recirculated to the cracking zone.

In various catalytic conversion processes it is important for economic reasons to recircula-te catalyst to the conversion zone. However, in many instances the catalyst in its form as recovered from efiiuents is not best suited for recirculation to the conversion zone due to adverse eifects of by-product materials, associated therewith, on the conversion reaction and/ or on the catalyst life.l Thus, in the conversion of hydrocarbons, such as in uid catalytic cracking, nely divided catalyst, in varying amounts dependent on the reaction conditions, is carried overhead from the cracking zone with vaporous eluent. In accordance with conventional practice that eiiluent is subjected to a scrubbing step separate from, or in a lower section of, an eifluent fractionation zone, wherein a scrubbing liquid is contacted undercondensing conditionswith theeiuent so that the heaviest components in the efliuent In another aspect this invention relates to the nited States Patent() 2,879,224 Patented Mar. 2,4, 1959 ICC f 2 stream are condensed, and catalyst particles entrained therewith are settled with the resulting condensate lto form a catalyst slurry, This `slurry can vber-eturned -to Ht-he` crackingzone but it contains an undesirable -cracking stock, becausegthe oil-isa high-coke*yielding'productv uri-- der conditions of cracking -and Vis converted 'into unduly:

large proportions of additional coke and/ or carbonaceous deposits on the catalyst particles. Thus, generally, the catalyst lparticles entrained in the vaporous reaction product are recovered as a slurry in the bottomsin'the" fractionator and because the bottoms product vis high ycokeyielding under cracking conditions, it is disadvantageously' recirculate'd to the cracking step. Thus, it is important that, prior to recirculating the catalyst to the cracking zone, it be separated from the said high coke-yielding oil by-product.

This invention providesforeffecting separation of finely divided solids from their association with a fluid unsuitl able therefor, the solids being recoverable alone onpreterably as a slurry inconjunction with a ilushing or displacing tiuid by which the iluid, initially in contact with the solids, has been replaced. When desired, the ushing uid is selected so as to be separable from the catalyst ultimately in `Contact therewith by any suitable means, as for example, distillation.

In accordance with this invention particulatesolidsare separated from admixture with a fluid unsuitablev asa component of said adrnixtureby passing intoa body of such solids and uid, a different fluid suitable for such admixture, inuniform contact therewithunder .conditions so as. to permit settling of solids and replacement .of the unsuitable uid with the suitable fluid, such asby effecting countercurrent flow contact of added iiuid with saidd'luidsolids `body under time .conditions and rate ofvertical linear ow to permit said settling and said replacement, or by passing a body of said solids-huid into a `settler and introducing the displacing iluid upwardly into the said solidsefluid body at a rate .so as to not preclude settling of solids but so as to effect replacement of the initially present uid with the added uid. Settled solids are-re- Icovered either as a slurry with the added uid, substantially free from fluid initially in admixture therewith, or, dependent on the time of settling, as a susbtantially fluidl free mass. When desired, settled solids can bey separated from residual lluidlin contact therewith by any desired means, preferably by distillation. Such an embodiment is advantageously applied when the iluid initially associated with the solids is difficultly separable therefrom. This embodiment iS, accordingly, advantageouslyvapplied to the separation of fluid from a fluid-solids mass,4 which uid is not stable at-its-potential distillation-temperatures and, if distillation is attempted, residual vdecomposition products depositen the solids surface.

Further, in accordance with this invention, particulate catalyst recovered from a catalytic conversion systern,in admixture with undesirable oily by-product, is freed `from rthat by-product by passing a ibody of the catalyst and oily by-product in contact with a ilushing or displacingliquid, preferably in countercurrent ow relation, under contact conditions carefully controlled so as to replace oily by- 4product admixed with the catalyst, with ,they ilushing or displacing liquid, while at the same time permitting catalyst particles to settle, substantially free from-oily byfproduct, preferably as a slurry with replacing liquid-to facili tate further handling of the catalyst.

Stillfurther in accordance with this invention, a slurry of catalyst and by-product oil recovered from processing efuents from iiuid hydrocarbon catalytic cracking, the said by-product oil being high coke-yielding under conditions of the cracking and thereby rendering thersluigry unsuitable for recycle to the cracking step, .is passed into a settling zone and therein catalyst particles. are permitted to settle while at the same time a flushing oil, low cokeyielding under the said cracking conditions, is introduced into the slurry at a lower point therein and passed upwardly and laterally in said slurry so as to effect uniform,

contact :of added fluid with said slurry and so as to not preclude settling of thegcatalyst, whereby the high cokeyielding oil byproduct is replaced by the upwardly moving oil. The settled catalyst is substantially free from the-high coke-yielding -by-product and is in form of` a one embodiment, namely, that of separating catalyst.

from a `by-product oil in a catalytic hydrocarbon cracking system. Thus, a suitable hydrocarbon cracking stock such as a gas oil boiling in the range of 450 to 850 F. is introduced via line 1t) into reactor 11 in contact therein with a suitable cracking catalyst such as SuperFiltx-ol natural catalyst under cracking conditions as, for example, atemperature in the range of 875 to 940 F. for a suitable time such as from to 80 seconds whereby it is converted to cracking product. Catalyst partially spent inreactor 11 is withdrawn as a side stream via linez 12 andpassed into catalyst regeneration zone 13 together with air via linek 14 for combustion regeneration,

i.e.,i to remove carbonaceous materials from the catalyst surface to reactivate same.A Eflluent regeneration gas is passed from zone 13 via line 16.- Regenerated catalyst is withdrawn from zone 13 via line 17 and passedinto line 10 wherein it is passed together with charge into zo'ne 11. Conventional cyclone separator means 18 is employed in zone 13 to minimize ow of tine catalyst particles through line 16. Total vaporous eihuent is passed from zone 11 via cyclone separator 19 into eiuent line 21 and passed into ellluent fractionator 22, initially into a lower portion thereof wherein it is lirst scrubbed with a liquid cooled to a temperature suiciently low as to cause-condensation of the highest boiling vaporous components. These components, referred to hereinafter as high coke-yielding by-product oils, contain entrained therewith substantially all catalyst particles discharged with effluent via line 21. Thus bottoms in.

zone 22 comprises a slurry of cracking catalyst and high coke-forming by-product oil, i.e., which oil yields large amounts of coke under the cracking conditions in zone 11 and is, therefore, not desirable for recycle to zone 11. E'luents substantially free from catalyst are fractionated inthe remaining upper portion of zone 22 under conventionalA fractonating conditions therefor, to provide light hydrocarbon product 22', a light cycle oil product withdrawn via line 23` and a relatively heavy cycle oi] product withdrawn via line 24.

Catalyst slurry is withdrawn'from fractionator 22-via line 26 and in relatively small proportion is passed via line 25 and cooler 2S into zone 22 as `scrubbing liquid for effecting condensation of heavy by-product oils and forscrubbing catalyst particles for recovery in the slurry, as described.

Catalyst slurry from line 26, not passed into line 25, is introduced into settling zone 27 by way of line 28, feed well 29 and perforate plate 31. Settler 27 in conjunction with other elements shown and discussed hereinafter is typical of apparatus known in the art and ordinarily employed as a thickener, one such type being often referrednto asa Dorr thickener. d Launder 32, peripherally disposed about the inner side 'wall35 of the settler as- 4 sembly, is sloped downwardly toward decant oil outlet 34.

Attached to launder 32 isadjustable weir 33 which is maintained level to allow separated oil, as described hereinafter, to How evenly into the launder 32 throughout the periphery of the vessel. Catalyst slurry from line 28 in settler 27 is maintained therein under conditions so as to permit catalyst to settle from the oil in admixture therewith and to accumulate in a lower most portion of settler 27. Thus, in the further operation of settler 27, Scrapers 30 are rotated by shaft 30' to which a rotating force is applied, whereby the ow of settled catalyst together with liquid in admixture therewith is facilitated for withdrawal from the settler via cone 36.

If the conventional system above illustrated were employed, catalyst Withdrawn via cone 36, in form of a slurry, would comprise catalyst and oil by-product described above, thelatter being high coke-yielding under cracking conditions in zone 11 and being, therefore, not suitable for recirculation to zone 11 or to regeneration zone 13 as the case may be. It is, therefore, a feature of one form of this invention that the catalyst recovered in settler 27 is free from high coke-yielding oil by-products initially in contact therewith in line 28. Accordingly, a ilush or displacement oil such as a heavy cycle oil is introduced via line 37 into cone 36, preferably in the form of an atomized spray 38, and passed upwardly through settler 27 in contact with slurry therein from line 28 laterally and upwardly at an upward linear velocity carefully controlled so that settling of catalyst particles in settler 27 is not precluded but whereby high cokeyielding oil therein is displaced from its association with catalyst particles, by the flushing oil, and is driven toward an upper portion of settler 27 and maintained therein as a clear decant oil and ultimately withdrawn from settler 27 by way of overflow into launder 32 and withdrawn via line 34. Flush oil introduced via line 37 is a low coke-forming oil, that is to say, it yields only small amounts of coke under cracking conditions employed in zone 11. displace the by-product oil or in any event to wash it free from catalyst in contact therewith so that catalyst particles moved from settler 27 into line 39 are substantially free from the said by-product oil but are in admixture with at least a portion of the ush oil introduced via line 37,- as'a catalyst-flush oil slurry.

Catalyst-flush oil slurry is withdrawn via cone 36 andline 39 and recirculated to cracking zone 11 via line 41.

It is thus a feature of my invention that an admixture, or slurry, of'iinely divided solids with a fluid, is contacted with a liush or displacing luidunder specific countercurrent ow conditions by which an eicient separation of solids from the said uid is achieved. Thus, when slurry is withdrawn via line 39 and clear decant oil is withdrawn via launder 32, oil ush or displacement oil is introduced into the system via line 37 and slurry from zone 22 is introduced into settler via line 28, I have pro vided for separating nely divided solids from admixture with a iluid unsuitable as a component of such admixture, the contacting conditions being necessarily controlled at all times so asto effect the uniform contact of ushing oil with slurry while at the same time passing the flush oil into the said slurry at such a low predetermined rate of vertical linear ow that settling of solids particles is not precluded but whereby substantially complete replacement of fluid by the flushing fluid is achieved and solids withdrawn from the system are substantially free from uid initially in admixture therewith. Thus, in the practice of one form of this invention, flush oil is introduced into settler 27 at such a low rate that substantially complete displacement of fluid occurs in a central portion of settler 27 such as indicated by the' dotted line 40 which can be looked upon as an upper boundary of a zone of reflux, i.e., above which there is substantially only the displaced decant oil, i.e., the high The function of the tlush oil in settler 27 is toy cokeyielding oil from line 28 .which is.. u lti mat ely witlr drawn via launder 32 and conduit 34.

In the practice of the latter embodiment ,illustrated with reference to dotted line 40, a `minimum quantity of. ush oil is employed, and substantiallygno llushpil carried from the system in admixture withdecant -oil -via line 34.

In carrying out. this embodiment, Ait ispartiularlyimportant that the specific gravity of the iiushoil .employed be controlled to within a predetermined range as, v for example, from about 1.01 to. 1.3 times; thee specific gravitygof the high coke-yieldingoil contacted therewith. Thus, when the decant oil Ihas a speci'ricgravity a s for example, about 0.87 at 425 F., thelushfoilfshouldhave aspecic gravity of about 0.89 at v10,0 F. In thepractice of another form of this invention, if desired, vit isonly necessary that a sufficient amount of flush oil hereinployed so as -to wash the solids particlesfsnbstantially free from the liquid initially in contact therewith. In, that event, the decant oil is flushed from, contact withgsolids and removed from ,the settler but is accompanied` by an amount of ushing oil dependentupon the speciiicwashing conditions employed. In the practice of this embodiment, there is no line of demarcation such as represented by vdotted line 40 and althoughsome ilushingpil is `lost from the system via line 34, it is not necessaryl to effect control on the specific gravity of the displacing oil, `and a less valuable displacement oil may be utilized.

Any `suitable liush or displacementy fluid can be employed in the practice of this invention 'dependent, of course, upon the specific solids-Huidmixturetobe treated. However, any given flush or displacement Huid I`c3171 :be employed over a controlled range ofspeciiicgravity by merely adjusting temperature. thereof. .Euer nplaryof various ush uids that can be employed are light. cycle oils, heavy cycle oils, gas oils, or mixtures-thereof,

Temperatures employed .in effecting -thecountercurrent iiowy process of this invention are, of course, dependent upon the specific solids-huid (e.g., from line 289i., How.- ever, as applied to separation of solids fromslurry such as that in line 28 of the attached drawings, it is ,generally advantageous to employ a temperature in settler 27 .in the range of about 200 to 450 F. It is important that the rate of inflow of flush or displacementoil-to settler 27 be at all times controlled so that the lvertical linear velocity of the added oil does not exceedthat lwhich precludes settling of solids particles in zone 2,7. Thus, as `applied to the system illustrated, a vertical linear velocity of ush oil from line 37,y in settler27, ismain tained generally below about 1.0 :foot .per shouf when it is desired to effect substantially complete displacement of by-product oil in settler 27, i.e., without lthere-being displacement oil vwithdrawn via line 34. When-` itis intended that higher linear velocities betemployedsoias to eiect washing'of the solids particles with concomitant carry-over of displacement oil into conduit 34, vertical linear velocities of displacement oil infsettler 27'above about 1.0 foot per hour are employed.

It is an important feature of this invention that, as applied to catalytic cracking of hydrocarbons, ,a low carbon-forming oil, preferably having-its gravityadjusted by temperature control, is employed to displace high carbon-forming oil fromwithdrawn catalyst in-order `:that substantially no high coke-forming oil is returnedfto the cracking system with catalyst vto be recirculated thereto. The following tabulation is illustrative of one `set of conditions characteristic of operation of the embodiment described above with reference to -the drawings.

Slurry charge, line 28 F' 400-450 (a) Decanffoil b./h 1'00 Specific gravity at 425 F A0.87

(b) Catalyst, 2100 pounds or 0.5#/ gal1on. Flush oil, line 37 F-, v90-ll0 (a) Heavy cycle oil b./h Al0() Specific gravity at 100F. .0:89

Qhargetoreactor 1 1:

(a) Heavy cyclwlf-f-f--efv-h/h 907 (b) Catalyst, 205.4pounds or.0. 54#,/gal1on. Decantedoil, line 3 4 b./l 1 -100 It is `a further feature of this Yinvention thatl upon recovery of slurry such as from cone 36,1i.e., anys lurry of solids with flush or displacement iiuid,-altl iough it can be rccirculated lto the conversion system, can be resolved into the solidsv and fluid componentsV such as :by distilla' tion, thereby providing for an ultimate separation. of solids from fluid initially in contactA therewith.

Although the linearvelocity of llush oil passed throughy the settler is dependent upon the specific slurry, i;e., the specific high coke-formingoil, the specificV gravity ofthe catalyst particles, the specific flush oil employed andthe like, the linear velocity of flush oil introduced into the settler is generally within the range of vfrom 0.5 to 1.0 foot per `hour or about 0.5 to 1.0 cubic foot per cubic foot of slurry per square'foot of settling area per hour; a linear velocity of about one'r'oot-per'hour or about one cubic footof ilush oil per cubic foot ofvslurry per square foot of settling area per hour being often employed; Linearl velocities of displacing oil outside-the numericalrange stated with reference to treating a slurry from hydrocarbon cracking can be employed, particularly when the solids-huid mixture is from a source other than hydrocarbon cracking and particularly when yitv is in f act a non-hydrocarbon mixture.

Although I have .described my invention lin termsl of adding the displacing fluid, preferably as a spray, at a point in the cone ofthe settler system, as illustrated, the. displacing fluid can be introduced in any .desired manner so asto maintain the said iluid inuniform contact relation with theslurry to be treated. In one form, the displacing tluid can `be introduced into the settling zone at selected points as separate streams of' iinely divided particles, advantageously in an upward direction. Such an assembly of inlets in one form is a plurality `of spray nozzles extending laterally across -thesettling zone, spaced from the bottom thereof so as to permit settling of solids together with replacing liquid to a point below the inlet spray system.

In another embodimentdisplacing liquid can be introduced into the settler as a plurality of ystreams through a perforate plate, adapted to receive replacing iiuid from the fluid inlet conduit, the said perforate plate Ahaving progressively larger perforations from its central portion toward its outer extremities, all of relative size, sothat an upward uniform rate of flow of replacing liquid in the settler is achieved. f

Anysuitable displacing or `flush* oil can be employed. However, the light cycle .oil fraction withdrawn from fractionator 22 via line 23 can be employed in part or in whole as the said flushing oil. Light cycle oil in line 23 is preferably, for thisl purpose, passed first to steam stripper zone 20 wherein it is passed in countercurrent contact with steam, under stripping conditions, from line 20a, the latter then being passed to fractionator 22 via line Ztlb. Light cycle oil, steam stripped of light ends, and boiling generally within a range vof 400 to 650 F. is withdrawn from the system via line 23. Steam stripped light cycle oil from vessel 20 is advantageously employed as the iiush oil in line 37, alone or together with ilush oil from line 37 and/or a heavy cycle oil from line -24 as described hereinafter. Thus, Pwhen soy employed, steam stripped light cycle oil from stripper 20is admitted into line 37 via line 37a.

A heavy cycle oil fraction'recovered asa fractionation product in zone 22, withdrawn via. line 24, can be employed as a ush oil alone or together with light. cycle oil in line 37a and/or tiush oil introduced into line 37 via line 37e. Thus, when s0 relrlplyd,` ,heavy cycle oil inline 24 is passed to steam stripper 30" wherein it is passed in countercurrent contact with steam from line 30a under stripping conditions. Steam from zone 30' is passed together with light ends to fractionator 22 via line 30b. Heavy cycle oil, steam stripped of light ends, and boiling within a range of about 550 to 800 F. is withdrawn from stripper 30' via line 24.

Steam stripped heavy cycle oil from vessel 30"' can be advantageously employed as a displacing or ushing oil, alone or together with `ush oil from line 37c and/ or light cycle oil from stripper 20, as above discussed, being in that event introduced into line 37 via line 37b.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, drawing, and the appended claims to this invention, the essence of which is that (l) particulate solids are separated from a fluid in admixture therewith by passing into contact with a body of such solids and fluid, a flushing uid under conditions so as to permit settling of solids and replacement of the uid initially in contact with said fluid with the flushing iiuid, the said contacting being conducted in a manner such as by countercurrently contacting added fluid with the said fluid-solids body under time conditions and rate of vertical linear flow to permit said settling and said replacement, or, by passing a body of said solidsliuid to a settler and introducing the displacing fluid upwardly into the said solids-huid body at a rate so as to not preclude settling of solids but so as to effect replacement of the initially present iluid with the added iiuid; this invention being advantageously applied to the separation of particulate catalyst from a catalyst slurry recovered froma catalytic conversion step; and (2) in a preferred form, a slurry of catalyst and lay-product oil recovered from processing efiiuents from fluid hydrocarbon cracking, the said by-product oil being high coke-yielding under conditions of the cracking and thereby rendering the slurry unsuitable for recycle to the `cracking step, is passed into a settling zone and therein catalyst particules are permitted to settle while at the same time a flushing or displacing oil, low coke-forming under the said cracking conditions, is introduced into the slurry at a lower point therein and passed upwardly and laterally in said slurry so as to effect uniform contact of added oil with said slurry and so as to not preclude settling of the catalyst, whereby the easily cokable oil by-product is replaced by the upwardly moving oil and catalyst is settled substantially free from high coke-yielding oil by-product and is in form of a slurry with the added oil, the latter slurry being then advantageously withdrawn from the settling zone and passed to the cracking step.

I claim:

l. A process for the separation of particulate solids from admixture with a first fluid, comprising passing a body of such solids and said first uid into a settling zone under conditions therein for settling said solids, passing a different second fluid into said body of such solids and said first uid in uniform contact therewith and controlling the rate and amount of flow of said second fiuid into said body so as to maintain said settling and to replace said first fluid in said body, and recovering settled solids in admixture with said second huid from said settling zone substantially free from said rst Huid.

2: A process for the separation of particulate solids in admixture with a first uid not readily separable from said solids by ordinary distillation, comprising contacting the Vbody of solids and said first fluid in a settling zone withV a second fluid readily separable from said solids by distillation, so as to displace the said first uid from admixture with said solids, recovering said second uid in admixture with said solids, and separating the said second fluid from resulting contact with said solids.

3. The process of claim 2 wherein said second iluid in admixture with said solids is separated from said solids by distillation.

4; In a catalytic conversion wherein uid by-product of said conversion isfadmixed with particulate catalyst'A current contact ow relation with said admixture undertime conditions providing for replacement of said byproduct with replacing uid but permitting settling of said catalyst, whereby catalystsettles inl admixture with at least a portion of said replacing fluid, and recovering resulting catalyst in said replacing uid free from said by-product.

5. In the iiuid catalytic cracking of hydrocarbons, wherein a by-product oil` is formed and is recovered from the conversion zone together with catalyst as a slurry, and said catalyst is freed from said lay-product oil by contacting said slurry with an oil to replace said by-product oil, the improvement comprising passing the said replacing oil in uniform countercurrent contact flow relation with said slurry under controlled time conditions so as to cause separation of catalyst from said by-product oil and to cause catalyst thus' separated to settle together with at leasta portion of said displacing oil, and recovering resulting catalyst in said displacing oil free from said by-product.

6. The process vof claim 5 wherein catalyst thus separated and containing'said displacement oil is recycled as a slurry to the cracking zone.

7. In the iiuid catalytic cracking of hydrocarbons` wherein vaporous effluent contains suspended particles of catalyst together with by-product oil, wherein said byproduct oilI is recoveredf as a slurry with catalyst as a resultof processing of said effluents, the said by-product oil being high coke-yielding under the conditions of said cracking and thereby rendering the said slurry unsuitable for recycle to thecracking step, the improvement comprising passing said slurry into a settling zone and therein allowing catalyst particles to settle by gravitation, passing a flushing oil low coke-yielding under conditions of said'cracking, laterally and upwardly into said slurry atan initiallow A'point therein so as to effect uniform contact of flushing oil with said slurry at a rate of vertical linear ilow not pre'cluding settling of catalyst and providing for recovery of catalyst as a slurry with said flushing oil, separating settled catalystv substantially free from said high coke-yielding oil as a slurry with said flushing oil, and passing the last said slurry to the cracking system for reuse of said catalyst therein.

8. In the vapor-phase iiuid catalytic cracking of hydrocarbons wherein 'by-product oil, easily converted to coke under conditions of said cracking, is discharged together with catalyst in vaporous cracking eluent, and is recovered as a slurry with said catalyst, and wherein said byproduct oiliis tobe displaced from said slurry by a ilushing oil noti easily converted to coke under said cracking conditions, the improvement comprising introducing said ushing oil-into uniform countercurrent contact flow relationrwith said slurry, maintaining said uniform Contact under relative rates of flow of said slurry and ushing oil so that catalyst particles freed from said heavy oil are caused to settle in the zone of said contacting together with at least a portion of said fiushing oil, and passing settled catalyst 4together with flushing oil associated therewith as a recycle stream to the cracking system, whereby catalyst passed with eluent from said cracking is recycled to said cracking substantially free from high coke-yielding oil by-product initially associated therewith as described.

9. The improvement of claim 8 wherein said displacement of by-product oil with flushing oil takes place in a central zone of' reflux, above which substantially no flushing oil is present.

10. The improvement of claim 8 wherein said cracking eiiluent is distilled to produce distillate product and said slurry is recovered as residual product of said distillation, and wherein at least a portion of said distillate product is employed as said ushing oil.

11. The improvement of claim 10 wherein said distillate comprises a light cycle oil boiling in the range of about 400 to 650 F.

12. The improvement of claim 10 wherein said distillate comprises a heavy cycle oil boiling in the range of about 550 to 800 F.

13. In the vapor-phase uid catalytic cracking of hydrocarbons wherein by-product oil, easily converted to coke under conditions of said cracking, is discharged together with catalyst in vaporous cracking eluent, and is recovered as a slurry with said catalyst, and wherein said by-product oil is to be displaced from said slurry by a ushing oil not easily converted to coke under said cracking conditions, the improvement comprising passing said slurry into a settling zone, introducing said flushing oil as a spray into said zone at a point in a lower portion thereof, laterally and upwardly dispersing said flushing oil in said slurry to eiect uniform contact of ushing oil with said slurry, controlling the rate of llow of said flushing oil so as to not exceed that which precludes catalyst particles from settling in said settling zone, whereby said by-product oil is replaced by said ushing oil and catalyst particles free from said by-product oil settle as a bottom layer in said settling zone together with at least a portion of said ushing oil and wherein displaced -by-product oil substantially freed from catalyst forms a top layer in said settling zone, decanting catalystfree by-product oil from said top layer, and passing a stream from said bottom layer in settling zone as a recycle stream to said cracking.

14. Apparatus comprising a settling chamber; a iirst conduit means for introducing a rst uid containing solids into an upper portion of said chamber so as to form an upper layer of said first iluid within said chamber; a second conduit means for introducing a second fluid into said chamber at a point adjacent the bottom of said chamber so as to form a lower layer of said second iluid within said chamber; tluid dispensing means in said chamber connected with said second conduit means and adapted to disperse uid from said second conduit means upwardly and uniformly through the horizontal l cross-section of the lower portion of said chamber; a third conduit means connected with said chamber at a point above the point of introduction of said second cou-v duit means for withdrawing said irst uidfrom within said chamber free from admixture with said second fluid and with said solids; and a fourth conduit means connected with said chamber at a point below the point of introduction of said second conduit means for withdrawing said second uid containing said solids introduced into said chamber in admixture with said first uid and free from admixture with said first uid.

15. Apparatus of claim 14 wherein said dispersing means is a spray system for atomizing uid from said second conduit.

16. Apparatus of claim 14 wherein said dispersing means comprises a plurality of conduits disposed across the interior of said chamber and adapted to disperse Huid from said second conduit upwardly through said chamber.

17. Apparatus of claim 14 wherein said dispersing means is a perforate plate adapted to receive upwardly llowing uid from said second conduit, extending laterally across a central portion of the interior of said chamber, and wherein the perforations are of progressively larger cross section from a central portion of said plate to its outer extremities.

18. Apparatus of claim 14 containing scraper means adapted to be moved in a lower portion of said chamber so as to direct ow of fluid for withdrawal from said chamber through said fourth conduit.

References Cited in the le of this patent UNITED STATES PATENTS 530,897 McClelland Dec. 11, 1894 2,431,499 Palmer Nov. 25, 1947 2,447,149 Wier Aug. 17, 1948 2,483,706 Lind Oct. 4, 1949 2,537,904 McAllister Ian. 9, 1951 2,689,209 Blair Sept. 14, 1954 2,728,641 Thorp et al Dec. 27, 1955 

1. A PROCESS FOR THE SEPARATION OF PARTICUALTE SOLIDS FROM ADMIXTURE WITH A FIRST FLUID, COMPRISING PASSING A BODY OF SUCH SOLIDS AND SAID FIRST FLUID INTO A SETTLING ZONE UNDER CONDITIONS THEREIN FOR SETTLING SAID SOLIDS, PASSING A DIFFERENT SECOND FLUID INTO SAID BODY OF SUCH SOLIDS AND SAID FIRST FLUID IN UNIFORM CONTACT THEREWITH AND CONTROLLING THE RATE AND AMOUNT OF FLOW OF SAID SECOND FLUID INTO SAID BODY SO AS TO MAINTAIN SAID SETTLING AND TO RE PLACE SAID FIRST FLUID IN SAID BODY, AND RECOVERING SETTLED SOLIDS IN ADMIXTURE WITH SAID SECOND FLUID FROM SAID SETTLING ZONE SUBSTANTIALLY FREE FROM SAID FIRST FLUID.
 7. IN THE FLUID CATALYTIC CRACKING OF HYDROCARBONS WHEREIN VAPOURS EFFLUENT CONTAINS SUSPENED PARTICLES OF CATALYST TOGETHER WITH BY-PRODUCT OIL, WHEREIN SAID BYPRODUCT OIL IS RECOVERED AS A SLURRY WITH CATALYST AS A RESULT OF PROCESSING OF SAID EFFLUENTS, THE SAID BY-PRODUCT OIL BEING HIGH COKE-YIELDING UNDER THE CONDITIONS OF SAID CRACKING AND THEREBY RENDERING THE SAID SLURRY UNSUITABLE FOR RECYCLE TO THE CRACKING STEP, THE IMPROVEMENT COMPRISING PASSING SAID SLURRY INTO A SETTLING ZONE AND THEREIN ALLOWING CATALYST PARTICLES TO SETTLE BY GRAVITATION, PASSING A FLUSHING OIL LOW COKE-YIELDING UNDER CONDITIONS OF SAID CRACKING, LATERALLY AND UPWARDLY INTO SAID SLURRY AT AN INITIAL LOW POINT THEREIN SO AS TO EFFECT UNIFORM CONTACT OF FLUSHING OIL WITH SAID SLURRY ATA RATE OF VERTICAL LINEAR FLOW NOT PRECLUDING SETTLING OF CATALYST AND PROVIDING FOR RECOVERY OF CATALYST AS A SLURRY WITH SAID FLUSHING OIL, SEPARATING SETTLED CATALYST SUBSTANTIALLY FREE FROM SAID HIGH COKE-YIELDING OIL AS A SLURRY WITH SAID FLUSHING OIL, AND PASSING THE LAST SAID SLURRY TO THE CRACKING SYSTEM FOR REUSE OF SAID CATALYST THEREIN. 